I'm remodeling my kitchen and have 2 questions regarding the reinstallation of the sink/disposal/dishwasher:

1. The old dishwasher had its own dedicated drain outlet & did NOT drain into the disposal or directly to the sink drains. Is this arrangement preferable to connecting the d/w drain to the disposal? If so, how would I connect the 1" (inside diameter) rubber drain hose from the d/w to the 1-7/8 (outside diameter) black ABS waste pipe?

2. Is it preferable to use metal or plastic for the drainpipes between the sink/dishwasher and the waste outlet?